Welcome to a potentially frustrating journey. Like I said earlier, there are basics to shooting minies. Bullet/bore windage, cap type, powder type (real black v "substitutes"), powder brand (Goex v Schutzen), powder granulation (2f v 3f), lube type, lead alloy, casting methodology.
25 rounds is a bare minimum to be able to even begin to go through variables that affect accuracy. Add to that, you have to segregate by weight. I trust only ONE person for precast and that Pat aka CivilWarBulletman, and he has a page with Lodgewood. It's easy to get voids in a minie when casting and they have to be cast hot with the lead at 800+F.
Type and brand of powder can affect results. I've had overall best results with Old Eynsford, but again, that's a variable from gun to gun. Now to cap type. I've seen very minor differences between RWS and Schutzen caps. With CCI caps, results were erratic and groups opened way up. Reason is, the CCI caps USED to be the gold standard till some reenactor had an eye injury and sued CCI so they changed the caps for the worse. Avoid CCI.
Next thing to look at is lube. Many use plain Crisco, but there is much, much better out there and it DOES affect accuracy. Again, when varying powder charge weight, powder type, powder brand and lube type, 25 is hardly enough for any conclusive results. I've done extensive experimentation with these variables and have seen two guns, supposedly identical, like completely different loads. Back to lube, after more than a few rounds downrange testing lubes, with all other variables held constant, I'm set with two. One is Len's Lube a commercial concoction and it's only for shooting the "trashcan" style minie. The other is a mix of beeswax, lard, and lanolin.
Here's a pic of what the beeswax/lard/lanolin does in my Parker Hale. Load is 42g 3f Old Eynsford, RCBS Hogdon, RWS caps-
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And what the Len's does in my 1862 Colt contract. Load is 44g 3f Old Eynsford, Rapine Trashcan, RWS caps
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